Copolymers of poly(ethylene terephthalate) (referred to sometimes herein as PET) with various dicarboxylic acids are well known in the art. Examples are U.S. Pat. Nos. 3,625,409; 3,669,921; 3,733,309; 3,932,358; 3,948,859; and 3,966,836. With the exception of U.S. Pat. No. 3,733,309 most of these deal with low molecular weight and low-melting copolyesters. Other patents of interest are U.S. Pat. Nos. 4,115,363; 4,145,517; 4,076,693; 4,049,631; 4,098,769; and 4,100,303.